Automatic disconnection by “BLE_HCI_CONN_INTERVAL_UNACCEPTABLE”

[takashina hiroki]

I have a question about “BLE_HCI_CONN_INTERVAL_UNACCEPTABLE”.

SDK: 15.3.0
Example: ble_app_multirole_lesc (source changed from sample)
Device: EYSHJNZWZ (nRF52832)

The device is operating as "Central".
After connecting with "Peripheral", "Peripheral" is disconnected after 4 minutes 30 seconds.
The disconnection factor is "BLE_HCI_CONN_INTERVAL_UNACCEPTABLE".
Please tell me about the cause of the disconnection.

[Susheel Nuguru]

This only happens when you get a BLE_CONN_PARAMS_EVT_FAILED which means that the connection param update procedure has failed. Your application must then retry the request with other parameter values. Here is a bit old thread but still with valid information on how the connection param update work on central and peripheral side..

[takashina hiroki]

Thank you for answering.
I will check it.

Please tell me one more thing.
Who sets 4 minutes and 30 seconds? ("Central" or "Peripheral")
And, Please tell me how to set it.

[takashina hiroki]

I can't confirm because I don't have a sniffer.
Is there any other way to check the cause?

[takashina hiroki]

I thought that this would happen if the connection parameters were not updated within "C_BLE_CONN_PARAMS_MAX_UPDATE_COUNT (= 3)" times.

That is, after 65 seconds (
= C_BLE_CONN_PARAMS_FIRST_UPDATE_DELAY (= 5s)
+ C_BLE_CONN_PARAMS_NEXT_UPDATE_DELAY (= 30s)
+ C_BLE_CONN_PARAMS_NEXT_UPDATE_DELAY (= 30s)
)

Is my idea wrong?

[Susheel Nuguru]

takashina hiroki said:

I can't confirm because I don't have a sniffer.

 If you have any Nordic DK, then you can make it to work as the BLE air sniffer. Please download the software here ad follow the guide here.

It is important that you know understand how your device is behaving in air to debug issues like this.

[takashina hiroki]

I don't have a Nordic DK.
Therefore, it cannot be confirmed by that method.
Is there any other way to check the cause?

If disconnected, how many seconds later will it theoretically disconnect?
4 minutes and 30 seconds later? 65 seconds later?

[Susheel Nuguru]

There are many reasons that the device could get disconnected.

If the disconnect is initiated in ble_conn_params.c after C_BLE_CONN_PARAMS_MAX_UPDATE_COUNT failed attempts then it should have been after C_BLE_CONN_PARAMS_NEXT_UPDATE_DELAY + C_BLE_CONN_PARAMS_NEXT_UPDATE_DELAY + C_BLE_CONN_PARAMS_FIRST_UPDATE_DELAY = 1 minute and 5 seconds later.